def main():
A=[0]*4
X=A*4
B=[A]*4
C=[A[:]]*4
D=[[0]*4]*4
print("A=",A)
print("X=",X)
print("B=",B)
print("C=",C)
print("D=",D)
B[1][1]=2
print("B=",B)
C[1][1]=2
print("C=",C)
D[1][1]=2
print("D=",D)
print("B[1]=",B[1])
print("C[1]=",C[1])
print("D[1]=",D[1])
Mat=[]
i=0
while i<4:
lin=[]
j=0
while j<4:
lin=lin+[0]
j=j+1
Mat=Mat+[lin]
i=i+1
print("mat=",Mat)
print("mat[1]=",Mat[1])
mat[1][1]=2
print("mat=",Mat)
#---------
main()